On July 5, the Tokyo District Public Prosecutors Office brought a summary indictment against the Japanese advertising giant on charges of violating the labor standards law. But the court judged the prosecutors' action to only demand a fine was inappropriate.

It is rare for a summary court to reverse a decision by public prosecutors, sources familiar with the matter said.

The first hearing on the overwork problem at Dentsu, which came to light following the work-related suicide by a young female employee in December 2015, will be held at the summary court.

Usually a summary court orders payment of fines up to ¥1 million in a summary trial after only examining documents. But under the criminal procedure law, if a judge finds a summary indictment inappropriate, an open trial should be held.